What is the best way to breed bettas and how long do they have to be together

Put the male in the breeding tank. Leave him there for a day or so. Keep the female in sight. Keep the water clean by fishing out whatever he doesn't eat within a minute or two of giving it to him. He ought to build a nest. Keep feeding the girl, too.

Once he's settled in and everything, bring in the clear, fish-safe tube and put it in the tank with the male, away from the nest. He should be outside of it. Deposit the female on the inside. Give them a few hours to make faces at each other. From now on, the male should get NO FOOD untill you take him out.

After they get to know each other, take the tube out, letting the female into the rest of the tank. There will be some chacing and biting, but she should eventually inspect the nest. If there is more biting than anything else, put the girl back in the tube and try again later.

Eventually they will settle in and mate. A light should be left on at all times on the breeding tank untill the male is removed. Mating will take up to a few hours, and the female should be removed once it is over.

The light should be left on, and the male will take care of the fry on his own for a while. It looks like he's eating them, but he's just spitting them back into the nest.

Once the fry are trying to swim along on their own in a normal fish orientation (horizontal) you should take dad out and start feeding them, if not a little sooner. You might need a magnifying glass to see the little things.

Keep them clean and fed, and in enough water. You may need to move some into another, similarly set up tank if you have a really big spawn with a lot of fry. In a few months you should be able to start seeing the males develop pretty colors and fins. Once they start getting agressive, seperate them. The girls can be kept together.